Blade support limb for vertical axis wind turbine

ABSTRACT

A blade support limb structure of vertical axis wind power generator includes a fixed support limb ( 1 ) and a rotatable support limb ( 2 ), one end ( 21 ) of the rotatable support limb is connected with one end ( 22 ) of the fixed support limb and the rotatable support limb may rotate around it. The structure keeps a wind wheel at stable rotation speed in the case of environmental wind speed exceeds rated wind speed, thereby to ensure that vertical axis wind power generator outputs constant power. The structure solves a problem of constant power output of vertical axis wind power generator from hundreds watt to thousands watt, so its applications are wide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/CN2007/001984 with an international filing date of Jun. 25, 2007, designating the United States, now pending, and further claims priority benefits of Chinese Patent Application No. 200610117017.0 filed Oct. 11, 2006. The contents of all of the aforementioned specifications, including any intervening amendments thereto, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a blade support limb, and particularly to a blade support limb for a vertical axis wind turbine.

2. Description of the Related Art

Vertical axis wind turbines are widely used for generating power and each comprises a wind rotor. However, there is a none-neglectable problem with existing vertical axis wind turbines: as an ambient wind speed is greater than a rated wind speed, a power output of a wind rotor correspondingly increases, as the ambient wind speed is far greater than the rated wind speed, the wind rotor is incapable of operating.

Normally, the blade is installed at a cantilever support limb (or cantilever support or blade support limb) or ring support and cannot rotate relative to the blade support limb, i.e. a fixed support limb structure with constant blade rotation angle α, one end of the blade support limb is connected with the blade, and other end of it is connected with the vertical axis.

For the effect of blade rotation angle α on the rotation speed of the wind rotor of vertical axis wind turbine, please refer to the Chinese Patent Public No. CN1831330A and another separate Chinese Patent Application No. 200610028267.7 applied by the inventor.

When blade rotation angle α is small, the wind rotor can get relatively high rotation speed and wind energy utilization ratio. For vertical axis wind turbine with constant blade rotating angel α, the rotation speed of its wind rotor is proportional to the environmental wind speed. Under constant blade rotation angle α, the higher the environmental wind speed is, the higher the rotation speed of wind rotor is. The wind energy is proportional to the cube of the environmental wind speed. when the environmental wind speed increases from 10 m/s to 25 m/s, the wind energy increases by nearly 16 times. Therefore, vertical axis wind turbine needs to have a motor with relatively high power to match with the wind rotor so that it can maintain operation under a relatively high environmental wind speed. And thus the designed rated wind speed of the vertical axis wind turbine must be very high. However, considering the characteristics of a motor, if the rated wind speed is high, the power will be very low under a low wind speed. And there are mostly low wind speeds under natural state, which thus decreases the efficiency of the vertical axis wind turbine. To enable the vertical axis wind turbine to maintain the rated output power within a relatively wind range of wind speeds, the wind rotor must still maintain a relatively constant rotation speed and output power after the environmental wind speed exceeds the rated wind speed so as to enable the vertical axis wind turbine to maintain operation under a relatively wide range of wind speeds and thus to enhance the value of vertical axis wind turbine.

Existing schemes overcoming such technical defects are to increase load resistance for small wind turbine with hundreds watt, apply “yawing and adjusting the pitch of blades” to large horizontal axis wind turbine and change angle of attack for large vertical axis wind turbine. Please refer to the Chinese Patent Public No. CN1831330A and another separate Chinese Patent Application No. 200610028267.7 applied by the inventor. However, considering the costs, such schemes are not suitable to vertical axis wind turbine from several kilowatts to dozens of kilowatts.

SUMMARY OF THE INVENTION

This invention is specific to the deficiency in existing technology and overcomes the design defects of existing vertical axis wind turbine, proposing a blade support limb structure of vertical axis wind turbine. The structure solves a problem of constant power output of vertical axis wind turbine from several watt to dozens watt or even hundreds kilowatt and is applied to small vertical axis wind turbine with hundreds watt in place of current coarse method of unloading load resistance, so its application is wide.

The specific technical scheme of this invention is described below:

A blade support limb structure of vertical axis wind turbine includes a fixed support limb (1) and a rotatable support limb (2), one end (21) of the rotatable support limb is connected with one end (12) of the fixed support limb and the rotatable support limb may rotate around it.

There is a gyration center axis (3) at the connection of one end (21) of the rotatable support lime and one end (12) of the fixed support limb, and the rotatable support limb (2) may rotate around it.

A control component (4) is connected at the other end (22) of the rotatable support limb, which is used to control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3). The control component is connected with one end (12′) of the fixed support limb adjacent to the rotatable support limb, by means of which a number of control components (4) is arranged orderly along the single direction of the wind rotor.

There is a control component (4) at one end (12) of the fixed support limb, which is used to control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3).

There is a control component (4) at one end (21) of the rotatable support limb, which is used to control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3).

Both ends (41) (42) of the control component respectively control one end (21) of the rotatable support limb and one end (12) of the fixed support limb and control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3).

The control component (4) is one or more kinds of flexible component, hydraulic component and electrical component.

There is a stop slot or stop pin at one end (12) of the fixed support limb, which is used to confine the rotation angle (β) of the rotatable support limb (2).

The length ratio of the rotatable support limb (2) and the fixed support limb (1) is 1:9˜9:1.

The length ratio of the rotatable support limb (2) and the fixed support limb (1) is 1:1.

The other end (11) of the fixed support limb is connected with the vertical axis (7).

The other end (11) of the fixed support limb is connected with the flange on the vertical axis (7).

The other end (22) of the rotatable support limb is connected with blade (6).

The other end (22) of the rotatable support limb is fixed with blade (6)

Through improving the blade support limb structure, this invention keeps a wind wheel at stable rotation speed under the condition that the environmental wind speed exceeds the rated wind speed, thereby to ensure that vertical axis wind turbine outputs constant power.

This invention will be described below on the basis of attached drawings and method of implementation.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description will be given below with reference to accompanying drawings, in which:

FIG. 1 is the structural diagram of blade support limb in existing technology.

FIG. 2 is the schematic diagram of fixing and installing blades in existing technology.

FIG. 3 is the structural diagram of blade support limb in this invention.

FIG. 4 is the schematic diagram of forces acting the blade support limb in this invention.

FIG. 5 is the schematic diagram of the positions of the initial angle β1 and rotation angle α1 of the blade support limb in this invention.

FIG. 6 is the schematic diagram of the positions of the initial angle β2 and rotation angle α2 of the blade support limb in this invention.

FIG. 7 is the enlarged view of the connection component of the blade support limb in this invention.

FIG. 8 is the enlarged view of the connection component of the blade support limb in this invention.

FIG. 9 is the structural diagram of another blade support limb in this invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following implementation examples give a further detailed description of this invention, but are not a limitation of this invention.

Example 1

FIG. 3 is the blade support limb structure of vertical axis wind turbine in this invention. The other end (11) of a fixed support limb (1) is fixed with the flange on the vertical axis. One end (21) of a rotatable support limb (2) is connected with one end (12) of the fixed support limb, and may rotate around one end (12) of the fixed support limb. The other end (22) of the rotatable support limb is fixed with blades. There is a gyration center axis (3) at the connection of one end (21) of the rotatable support limb and one end (12) of the fixed support limb, and the rotatable support limb may rotate around it. There is a control component (4) at one end (12) of the fixed support limb, which is used to control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3). Both ends (41) (42) of the control component respectively control one end (21) of the rotatable support limb and one end (12) of the fixed support limb and control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3). The control component (4) is flexible component (may also be replaced by hydraulic component or electrical component, which needs only to control the changes of the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3)). There is a stop slot (may also be replaced by stop pin) at one end (12) of the fixed support limb, which is used to confine the rotation angle (β) of the rotatable support limb (2) to change within certain controlled range, which plays a further role of getting stable and safe operation of the blade support limb structure in this invention. FIGS. 7 and 8 are the enlarged view of the connection component of the blade support limb in this invention.

As shown in FIGS. 4, 5 and 6, the initial angle of the rotatable support limb is β1. There is a flexible component (4) (press spring stacks) at the fixed support limb (1) of one end of stop slot (5). Since the concave face of the blade faces outside and the blade has a fixed rotation angle α1 at the initial position, a driving force of rotating around the vertical axis is produced on the blade under the driving of wind. FIG. 4 is the schematic diagram of forces acting the blade support limb in this invention. when the wind rotor rotates under a wind speed less than the rated wind speed, the restoring torque of the press spring L1*F1 (L1 is the arm of force of the press spring rotating around the gyration center axis (3), F1 is the force impact on the press spring) is larger than the centrifugal torque F2*L2 (L2 is the arm of force of the blade rotating around the gyration centre axis, F2 is the force impact on the blade) on it. The rotatable support limb is confined by the stop slot (5) at the initial position, i.e. the rotation angle β1 between the fixed support limb (1) and the rotatable support limb (2) keeps unchanged, and the rotation angle α1 keeps unchanged. The initial angle β1 between the fixed support limb and the rotatable support limb is relatively large so that the wind rotor can get a relatively large centrifugal force during the rotation. The optimal length ratio of the fixed support limb (1) and the rotatable support limb (2) is about 1:1, then the blade can get a relatively large centrifugal force and the rotation angle α1 can also change synchronically with β1. When the length ratio of the rotatable support limb (2) and the fixed support limb (1) is 1:9, β changes by only a very small angle, then a can reach the required angle. However, when the length ratio of the rotatable support limb (2) and the fixed support limb (1) reaches 9:1, β needs to change relatively greatly, then α can reach the required angle. The extreme condition is that the rotatable support limb is directly installed on the flange and the fixed support limb is omitted, the principle of which is similar to changing the angle of attack of the angle. Therefore, the optimal length ratio of the fixed support limb (1) and the rotatable support limb (2) is about 1:1, the blade can get a relatively large centrifugal force and rotation angle α1 can change synchronically with β1.

As the environmental wind speed exceeds the rated wind speed, the rotation speed of the wind rotor continuously increases along with the increase of wind speed. When the wind speed exceeds the rated wind speed, and then the rotation speed also exceeds the rated rotation speed, the restoring torque of press spring L1*F1 is less than the centrifugal torque L2*F2. Under the impact of the centrifugal torque, the rotatable support limb (2) rotates around its gyration center axis (3) and along with the rotating direction of the wind rotor. since the blade is fixed with the rotatable support limb (2), as the wind speed, the rotation speed and the centrifugal force increase, the angle β1 between the rotatable support limb (2) and the fixed support limb (1) gradually decreases to β2, equal to changing the blade rotation angle α1, getting the rotation angle of the blade to change from relatively small positive angle to negative one, i.e. the blade rotation angle α1 changes from positive angle to negative angle α2, as is shown in FIG. 6. For the application of changing the blade rotation angle, please refer to the Chinese Patent Public No. CN1831330A and another separate Chinese Patent Application No. 200610028267.7 applied by the inventor. For vertical axis wind turbine with the concave face of blade facing outside, when blade rotation angle is less than 2 degrees, the rotation speed and power of the wind rotor will decrease. Through computer simulative calculation (CFD), when the blade rotation angle changes from a positive value to a negative one, the rotation speed and torque of the wind rotor will decrease rapidly. Moreover, the smaller the negative value of the blade rotation angle is, the more rapidly the rotation speed decreases. When the negative value is less than a certain value, the torque direction of the wind rotor changes and the wind rotor gradually slows down. When the rotation speed of the wind rotor decreases, the rotatable support limb restores to the initial position under the impact of the restoring torque of the press spring. This forms a continuous cycle and thus maintains a stable rotation speed and power of the wind rotor when the wind speed exceeds the rated wind speed.

Example 2

For the blade support limb structure in Implementation Example 1, it is set as the prerequisite that the wind rotor with the diameter 1.36 m consists of blades of Goe63 airfoil, the length ratio of fixed support limb and rotatable support limb is 1:1, and the rated wind speed is 10 m/s, i.e. the wind speed of such device begins to affect the vertical axis wind turbine from 10 m/s. Through CFD, when the wind speed increases from 10 m/s to 15 m/s, 20 m/s and 25 m/s, the output power increases respectively from 170 watt to 210 watt, 220 watt and 230 watt. But the output power will increase from 170 watt to about 2660 watt without the blade support limb structure in this invention.

CFD calculation table Wind speed 10 m/s 15 m/s 20 m/s 25 m/s Power output by using existing 170 350 1360 2660 blade support limb structure (watt) Power output by using the blade 170 210 225 230 support limb structure in this invention (watt)

Example 3

Also for the blade support limb structure in Implementation Example 1, wind tunnel tests are performed by means of the same wind rotor and parameters. It is set as the prerequisite that the length ratio of fixed support limb and rotatable support limb is 1:1, when the wind speed increases from 10 m/s to 15 m/s, 20 m/s and 25 m/s, the output power of the motor increases respectively from 158 watt to 193 watt, 198 watt and 202 watt. But the output power of the motor will reach about 2600 watt without such device.

Table of wind tunnel tests Wind speed 10 m/s 15 m/s 20 m/s 25 m/s Power output by using 160 570 1320 2600 existing blade support limb structure (watt) Power output by using 158 193 198 202 the blade support limb structure in this invention (watt)

Example 4

FIG. 9 is the structural diagram of another blade support limb in this invention.

A control component (4) is connected with the other end (22) of the rotatable support limb, which is used to control the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3). The control component is connected with one end (12′) of the fixed support limb adjacent to the rotatable support limb, by means of which a number of control components (4) is arranged orderly along the single direction of the wind rotor. The control component (4) is flexible component (may also be replaced by hydraulic component or electrical component, which needs only to control the changes of the rotation angle (β) of the rotatable support limb (2) around the gyration center axis (3)). There can also be a stop slot (5) (may also be replaced by stop pin) at one end (12) of the fixed support limb, which is used to confine the rotation angle (β) of the rotatable support limb (2) to change within certain controlled range, which plays a further role of getting stable and safe operation of the blade support limb structure in this invention. By the blade support limb structure in this Implementation Example and the wind tunnel tests in Implementation Example 2 and 3, this invention manages to solve the problem of constant power output.

From these implementation examples we can get that the blade support limb structure in this invention overcomes the design defects of existing vertical axis wind turbine, thereby solves a problem of constant power output of vertical axis wind turbine from several watt to dozens watt or even hundreds kilowatt and is applied to small vertical axis wind turbine with hundreds watt, so its application is wide.

In spite of a detailed description of this invention and some implementation examples, it is evident that the skilled technicians in this field may make changes and amendments, but the inventor's idea and scope of design shall be followed. 

1. A blade support limb for a vertical axis wind turbine, comprising a plurality fixed support limbs (1) each having one end (12); a plurality rotatable support limbs (2) each having two ends (21) and (22); a central axis (3); and multiple control devices (4) each having two ends (41) and (42); wherein the end (21) of said fixed support limb (2) is connected to the end (12) of said fixed support limb, and is capable of rotating with respect to the end (12) of said fixed support limb(2); said central axis (3) is disposed at the connection between the end (21) of said rotatable support limb (2) and the end (12) of said fixed support limb (1); said rotatable support limb (2) is capable of rotating with respect to said central axis (3); said control device (4) is connected to the end (22) of said rotatable support limb (2), and to an end (12′) of a fixed support limb (1) adjacent to said rotatable support limb (2); the end (41) of said control device (4) controls the end (21) of said rotatable support limb (2) and the end (42) of said control device (4) controls the end (22) of said rotatable support limb (2) so as to control a rotation angle (β) of said rotatable support limb (2) with respect to said central axis (3); and said control devices (4) are one or more of elastic components, hydraulic control devices and electrical control devices.
 2. The blade support limb for a vertical axis wind turbine of claim 1, wherein multiple stop slots are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12).
 3. The blade support limb for a vertical axis wind turbine of claim 1, wherein multiple stop pins are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12).
 4. The blade support limb for a vertical axis wind turbine of claim 1, wherein a ratio between a length of said rotatable support limb (2) and that of said fixed support limb (1) is between 1:9 and 9:1.
 5. A blade support limb for a vertical axis wind turbine, comprising a plurality fixed support limbs (1) each having one end (12); a plurality rotatable support limbs (2) each having two ends (21) and (22); a central axis (3); and multiple control devices (4) each having two ends (41) and (42); wherein the end (21) of said fixed support limb (2) is connected to the end (12) of said fixed support limb, and is capable of rotating with respect to the end (12) of said fixed support limb(2); said central axis (3) is disposed at the connection between the end (21) of said rotatable support limb (2) and the end (12) of said fixed support limb (1); said rotatable support limb (2) is capable of rotating with respect to said central axis (3); said control device (4) is disposed on the end (12) of said fixed support limbs (1); the end (41) of said control device (4) controls the end (21) of said rotatable support limb (2) and the end (42) of said control device (4) controls the end (22) of said rotatable support limb (2) so as to control a rotation angle (β) of said rotatable support limb (2) with respect to said central axis (3); and said control devices (4) are one or more of elastic components, hydraulic control devices and electrical control devices.
 6. The blade support limb for a vertical axis wind turbine of claim 5, wherein multiple stop slots are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12).
 7. The blade support limb for a vertical axis wind turbine of claim 5, wherein multiple stop pins are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12)
 8. The blade support limb for a vertical axis wind turbine of claim 5, wherein a ratio between a length of said rotatable support limb (2) and that of said fixed support limb (1) is between 1:9 and 9:1.
 9. A blade support limb for a vertical axis wind turbine, comprising a plurality fixed support limbs (1) each having one end (12); a plurality rotatable support limbs (2) each having two ends (21) and (22); a central axis (3); and multiple control devices (4) each having two ends (41) and (42); wherein the end (21) of said fixed support limb (2) is connected to the end (12) of said fixed support limb, and is capable of rotating with respect to the end (12) of said fixed support limb(2); said central axis (3) is disposed at the connection between the end (21) of said rotatable support limb (2) and the end (12) of said fixed support limb (1); said rotatable support limb (2) is capable of rotating with respect to said central axis (3); said control device (4) is disposed on the end (21) of said rotatable support limbs (2); the end (41) of said control device (4) controls the end (21) of said rotatable support limb (2) and the end (42) of said control device (4) controls the end (22) of said rotatable support limb (2) so as to control a rotation angle (β) of said rotatable support limb (2) with respect to said central axis (3); and said control devices (4) are one or more of elastic components, hydraulic control devices and electrical control devices.
 10. The blade support limb for a vertical axis wind turbine of claim 9, wherein multiple stop slots are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12).
 11. The blade support limb for a vertical axis wind turbine of claim 9, wherein multiple stop pins are disposed on the end (12) of said fixed support limb (1), and operate to restrain the rotation angle (β) of the rotatable support limb (12).
 12. The blade support limb for a vertical axis wind turbine of claim 9, wherein a ratio between a length of said rotatable support limb (2) and that of said fixed support limb (1) is between 1:9 and 9:1. 